Sudden oak death inspection getting a boost from growers

ODA pilot program helps mitigate Phytophthora from nurseries
Oregon Department of Agriculture

The final verdict is not in, but a pilot project started in 2007 directing Oregon nursery growers to proactively reduce the fungus that causes sudden oak death appears to be somewhat successful. The Grower Assisted Inspection Program (GAIP) is a systems approach to deal with Phytophthoras in general, including the sudden oak death-related P. ramorum. Results over the past couple of years from the volunteer program are detailed in a written analysis submitted by the Oregon Department of Agriculture for peer review and to hopefully be published in a scientific journal.

“We are now at the point where we can start analyzing some of the results collected under GAIP,” says Gary McAninch, supervisor of ODA’s Nursery and Christmas Tree Program. “For some of the participating nurseries, the data is showing very good results. In others, the results aren’t so clear. But at this point, we are very high on the Grower Assisted Inspection Program.”

A federal mandatory inspection and certification program conducted by ODA continues to keep nurseries and inspectors busy. As an alternative, GAIP is designed to empower nurseries to do their own inspections and adopt management practices that lessen the likelihood of finding P. ramorum and other Phytophthoras in that nursery. High risk nurseries are targeted under the program- primarily those that grow rhododendrons and camellias, and that ship out of state. GAIP uses a systems approach that has become increasingly common in other areas of agriculture. The principles of HACCP- Hazard Analysis and Critical Control Points- shift the emphasis of inspection from the end product to the process itself.

“So rather than looking at the plants at the shipping dock, this program looks at the way plant material is propagated, where nurseries are getting their plant material, how they are dealing with sanitizing the water they use, and those types of issues that might lead to a greater risk of plant disease,” says McAninch. “Best management practices for each critical control point have been developed. As part of the program, ODA inspectors audit the nursery to ensure they use those management practices.”

Currently, 17 nurseries voluntarily participate in GAIP, developing a “mitigation manual”- the nursery’s game plan for dealing with Phytophthoras. Oregon State University plays a critical role in educating nursery operators and their workers on the fungi- its biology, symptoms, and diagnosis. Training includes instruction on disease management and the specific regulatory aspects of P. ramorum.

Additional time and results may be needed before final conclusions are drawn, but GAIP has allowed ODA and OSU- as well as the industry- to learn much more about Phytophthoras and the steps most effective in mitigating against related diseases.

“Because of GAIP, we aren’t just looking at the end product, we are looking at the process,” says Nancy Osterbauer, manager of ODA’s Plant Health Program and author of the GAIP analysis submitted for review and publishing. “As a result, we are learning a lot more about sudden oak death.”

The qualitative analysis of GAIP draws several detailed conclusions. But the bottom line is one of hope for the nursery industry in its battle with the potentially-crippling plant disease.

“The analysis indicates that best management practices are effective in mitigating Phytophthora disease in nurseries,” says Osterbauer. “However, those practices must be unique to each nursery. Critical control points will vary depending on the type of nursery stock produced. No one size fits all.”

Osterbauer’s study of the GAIP participants indicates that rhododendron was found infected most often with Phytophthora. The type of nursery stock propagation system at each farm also appeared to affect the presence of the disease, with samples testing positive more often coming from farms growing predominately containerized nursery stock. Osterbauer writes:

“Our data suggest that aspects of containerized nursery stock production systems, such as the use of overhead irrigation, are more conducive to the development of Phytophthora disease problems. Thus, best management practices adopted by growers of containerized nursery stock may need to be different from those adopted by growers of field stock.”

The study also suggests that some GAIP nurseries need time to implement the best management practices that would mitigate Phytophthora, whether to fully train its employees about those practices or to purchase new equipment as part of its plan. Also noted is the extra time needed in some nurseries before the practices effectively reduce endemic populations of Phytophthora to low levels.

“It’s analogous to having a big ship going in one direction,” says McAninch. “You are turning the ship slowly as it pertains to the amount of disease present in the nursery. It takes time to clean the system. We think, if we give it another year or two, even those GAIP nurseries that have not seen positive results yet, will.”

ODA has completed more than half of this year’s nursery inspections as part of its annual regulatory program for P. ramorum, including sampling and certification of about 700 targeted nurseries as part of federal requirements. So far, P. ramorum has been detected in six nurseries- one more than all of last year but down from the dozen or so positive nurseries found annually a few years ago. Nurseries with  P. ramorum must isolate the disease, and destroy infected and susceptible plant material before ODA can declare them P. ramorum-free. Quick detection and eradication has kept Oregon’s nursery industry from being disrupted in the marketplace.

But wouldn’t it be better and more cost effective to prevent the disease in the first place through best management practices that address the most vulnerable points in the nursery production process? That’s precisely what GAIP is designed to do. Other states and the US Department of Agriculture are watching closely to see if Oregon’s pilot project might become a substitute for the current certification program.

For more information, contact Gary McAninch at (503) 985-4785.

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